FIGS. 1a and 1b show a stator assembly for an electric supercharger from which the invention has been developed. The electric supercharger (not shown) comprises a switched reluctance motor. The stator assembly 1 of the motor has six windings 3 arranged in three pairs (each pair comprising two windings 3A, 3B, 3C opposite one another for forming opposing poles). Each winding 3 is a coil of wire that is wrapped around a metallic core. Each winding 3 has an input termination 5 and an output termination 7 associated with it. These terminations are connectable to an energising source (not shown in FIG. 1a). In the stator assembly of FIGS. 1a and 1b, the terminations 5, 7 extend directly above each respective winding 3. The terminations 5, 7 are therefore arranged in a ring (formed of twelve terminations, in sequential pairs of input terminations 5 and output terminations 7 above each respective winding 3).
To control the energising of the windings, the stator assembly comprises a control module (indicated in general terms by reference numeral 9 and shown in FIG. 1b). The control module 9 includes a microprocessor (not shown) for determining and controlling the sequence of energising the windings 3, three power control modules 11A, 11B, 11C each being arranged to supply power to one of the pairs of windings 3A, 3B, 3C, and tracking 13 to connect each pair of windings 3A, 3B, 3C, to a respective power control module 11A, 11B, 11C. For the sake of clarity, only elements relating to one pair of windings 3B are shown in FIG. 1b (with the exception of all three power control modules 11A-C).
The tracking 13 (shown only in simplified form in FIG. 1b) is formed of three PCB layers stacked above one another, each layer being associated with a respective pair of windings 3A-C. Each layer has a first track 15 connecting together the input terminations 5 of a pair of windings, a second track 17 connecting together the output terminations 7 of the same pair of windings, and additional tracks 19 linking the I/O terminals of the respective power module 11A-C with the first and second tracks 15, 17.
Such a tracking arrangement is complex and may therefore add cost to the control module. Furthermore, the tiered tracking results multiple layers of PCB and therefore in a relatively thick control module which can be undesirable from a cost perspective and/or from the perspective of the PCB's interaction with surrounding components of the supercharger.